No sunscreen is foolproof--even when applied regularly

FITNESS CLINIC

The sun can wrinkle your skin, make you look older and give you skin cancer. You can't prevent sun damage just by slathering yourself with sunscreen.

More than 600,000 new cases of skin cancer will be diagnosed in the United States this year, largely because people do not know how to protect themselves from the rays.

When you work out in the sun, you are exposed to two types of sun rays: UVA rays, which primarily cause aging and wrinkling, and UVB rays, which go much deeper into the skin to cause cancer. However, both UVA and UVB rays can cause wrinkling, aging and cancer.

Modern sunscreens generally block the UVB rays without blocking UVA rays. However, some newer sunscreens contain UVA-blocking chemicals such as benzophenones and Parsol 1789.

Nevertheless, no sunscreen can block all the sun's rays; someone who uses sunscreen can still get skin cancer. The products also may give individuals a false sense of security. As a result, people stay in the sun too long, increasing the damage to their skin.

The best way to prevent sun damage is to avoid the sun. Tightly woven shirts and hats are better sun blockers than any sunscreen. A roofover your head is more effective.

Keep in mind most sunscreens come off with sweating, bathing or swimming. Apply another coat. If you apply a good sunscreen every day, 365 days a year, you will fix the sunscreen's chemicals to your skin, which will protect you even more.

Q: Is there any advantage for a competitive athlete to train in another sport?

A: Training is specific. Marathon runners should train by running. Bicycle racers should train by cycling. Cross-training has been proposed for competitive athletes only because of the following theory:

To improve, an athlete has to conduct very hard workouts, but thesedamage the muscles. Therefore, the athlete has to allow enough time for those muscles to recover before it is safe to exercise intensely again. According to the theory, if a runner wants to exercise the day after a hard workout, he or she could ride a bicycle while allowing the lower leg muscles to heal.

But it's not that simple. The best way to train for a sport is to use your muscles in exactly the same way you use them when you compete. After a hard workout, most competitive athletes choose to work out the next day -- but at a very slow pace.

Dr. Mirkin is a practicing physician in Silver Spring specializing in sports medicine and nutrition.